As one of measures to mitigate exhaustion of frequency resources in the future, the discussion about secondary usage of a frequency is under way. The secondary usage of a frequency is to use a part or all of a frequency channel preferentially assigned to some system secondarily by another system. In general, the system to which a frequency channel is preferentially assigned is called a primary system and the system that secondarily uses the frequency channel is called a secondary system.
A TV white space is an example of the frequency channel discussed for secondary usage. The TV white space refers to, among frequency channels assigned to a TV broadcasting system as a primary system, a channel that is not used by the TV broadcasting system depending on the region. By releasing the TV white space for secondary usage, efficient utilization of frequency resources can be realized. As specifications of the wireless access method of the physical layer (PHY) and the MAC layer to enable secondary usage of the TV white space, for example, a plurality of standard specifications like IEEE802.22, IEEE802.11af, and ECMA (European Computer Manufacturer Association)-392 (CogNea) is known.
The IEEE802.19 is currently working to allow smooth coexistence of a plurality of secondary systems using different wireless access methods. For example, Non-Patent Literature 1 below divides various functions needed for coexistence of secondary systems into three functional entities of CM (Coexistence Manager), CE (Coexistence Enabler), and CDIS (Coexistence Discovery and Information Server). CM is a functional entity that mainly makes a decision for coexistence. CE is a functional entity to be an interface that mediates instruction transmission or information exchange between CM and a secondary usage node. CDIS is a functional entity to be a server that manages information of a plurality of secondary systems in a unified manner. CDIS also has a neighbor discovery function which detects neighboring secondary systems that may interfere with each other.